1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) panel including multi scanning bands.
2. Description of the Prior Art
The advantages of the liquid crystal display (LCD) include lighter weight, less electrical consumption, and less radiation contamination. Thus, the LCD has been widely applied to several portable information products, such as notebooks, PDAs, etc. The LCD gradually replaces CRT monitors of conventional desktop computers.
Generally speaking, the LCD comprises an upper panel, a lower panel, and a liquid crystal layer filled between the upper panel and the lower panel. The upper panel includes a common electrode and a plurality of color filters, and the lower panel includes a plurality of pixel electrodes, a plurality of thin film transistors, and a driving circuit. Furthermore, each of the pixel electrodes and the common electrode form a capacitor, and each capacitor and each thin film transistor together form a pixel unit with a matrix distribution.
Incident light will produce different polarization or refraction when the alignments of liquid crystal molecules are different, therefore, the LCD utilizes the potential difference between the pixel electrode and the common electrode to change the alignments of these molecules of the liquid crystal layer, and the liquid crystal molecules with different alignments are further used to control the light transmittance of each pixel unit so as to generate light beams with different intensities of gray level or to generate red, blue, and green lights with different brightness. Therefore, the LCD is enabled to produce gorgeous images.
FIG. 1 is a block diagram showing a prior art liquid crystal display and a driving circuit thereof. As shown in FIG. 1, a liquid crystal display panel 10 comprises a driving circuit (not shown in FIG. 1) and a plurality of pixel units (not shown in FIG. 1) with a matrix distribution. The driving circuit includes a plurality of scanning lines 12 used for transmitting scanning signals to each pixel unit and also includes a plurality of data lines 14 used for transmitting image data to each pixel unit. Therein, a plurality of rows of the pixel units are arranged on the display panel 10 respectively corresponding to the scanning lines 12, and a plurality of columns of the pixel units are arranged on the display panel 10 respectively corresponding to the data lines 14. A thin film transistor of each pixel unit is electrically controlled by both a scanning line and a data line and is driven by signals from the scanning line and the data line. Additionally, the scanning lines 12 horizontally arranged on the display panel 10 are electrically connected with a gate driver 16, and the data lines 14 vertically arranged on the display panel 10 are electrically connected with a data driver 18, which is further electrically connected with a signal supplier 20.
A conventional driving method of the prior art liquid crystal display panel 10 shown in FIG. 1 is described as follows. First, the image data is inputted from outside into the signal supplier 20, and then the image data is transmitted from the signal supplier 20 to the data driver 18. After that, a start signal is applied to the gate driver 18, and then the gate driver 18 supplies a first scanning signal to the first row scanning line 13 so as to turn on the thin film transistors electrically connected with the first row scanning line 13. The data driver 18 then uses the data lines 14 to transmit corresponding image data to the first row pixel units arranged on the display panel 10. Therefore, each of the first row pixel units is enabled to display an image.
When the application of the first scanning signal for the first row scanning line 13 is finished, the gate driver 16 supplies a second scanning signal to the second row scanning line 15. At this time, the thin film transistors electrically connected with the first row scanning line 13 are turned off while the thin film transistors electrically connected with the second scanning line 15 are turned on, and the data driver 18 uses the data lines 14 to transmit another corresponding image data to the second row pixel units arranged on the display panel 10. By way of the above-described method, the pixel units arranged on the display panel 10 are sequentially scanned from the first row to the last row. When the scanning of the last row pixel units is completed, a frame is completely displayed by the liquid crystal display panel 10, a scanning signal is applied to the first row scanning line 13 again, and so the next frame begins.
However, since the more scanning lines become required as the resolution of the liquid crystal display becomes higher, the time required for one frame scanning remains limited, and the scanning time of one scanning line is reduced. For a liquid crystal panel comprising 800 scanning lines and having a refresh frequency of 60 hertz (Hz), each scanning line has to finish scanning in 20.8 μs. When the number of scanning lines increases as 1080 for higher resolution, each scanning line has to finish scanning in 15.4 μs. Therefore, a scan delay easily occurs, and thus the image quality becomes worse. For the liquid crystal display panel of larger size, the scan delay is more obvious.
Another prior art liquid crystal display panel with dual scanning bands is developed for solving the above-mentioned problem. As shown in FIG. 2, the liquid crystal display panel 30 comprises a first scanning band 32, a second scanning band 34, a driving circuit (not shown in FIG. 2), and a plurality of pixel units (not shown in FIG. 2) with a matrix distribution. The driving circuit includes a plurality of scanning lines 36 positioned in the first scanning band 32 and used for transmitting scanning signals to each pixel unit of the first scanning band 32, and the driving circuit also includes a plurality of data lines 38 used for transmitting image data to each pixel unit of the first scanning band 32. As well, the driving circuit includes a plurality of scanning lines 40 positioned in the second scanning band 34 and used for transmitting scanning signals to each pixel unit of the second scanning band 34, and the driving circuit also includes a plurality of data lines 42 used for transmitting image data to each pixel unit of the second scanning band 34. The data lines 38 of the first scanning band 32 are disconnected from the data lines 42 of the second scanning band 34.
According to the position of the scanning line 36 and the scanning 40, a plurality of rows of pixel units are arranged respectively in the first scanning band 32 and the second scanning band 34 of the display panel 30. As well, according to the position of the data line 38 and the data line 42, a plurality of columns of pixel units are arranged respectively in the first scanning band 32 and the second scanning band 34 of the display panel 30. A thin film transistor of each pixel unit in the first scanning band 32 and the second scanning band 34 is electrically controlled by both a scanning line and a data line and is driven by signals from the scanning line and the data line. Additionally, the scanning line 36 horizontally arranged in the first scanning band 32 and the scanning line 40 horizontally arranged in the second scanning band 34 are simultaneously connected with a gate driver 44, while the data line 38 vertically arranged in the first scanning band 32 and the date line 42 vertically arranged in the second scanning band 34 are respectively connected with a first data driver 46 and a second data driver 48. The first data driver 46 and the second data driver 48 are electrically connected with a memory 50, which is further electrically connected with a signal supplier 52.
A conventional driving method of the prior art liquid crystal display panel 30 shown in FIG. 2 is described as follows. First, the image data is inputted from outside into the signal supplier 52, and then the image data is transmitted from the signal supplier 52 to the memory 50. The image data stored in the memory 50 is further transmitted to the first data driver 46 and the second data driver 48, respectively. After that, a start signal is applied to the gate driver 44, and then the gate driver 44 supplies a scanning signal to the first row scanning line 31 of the first scanning band 32 and also to the first row scanning line 41 of the second scanning band 34. Consequently, the thin film transistors electrically connected with the first row scanning line 32 of the first scanning band 32 and the first row scanning line 41 of the second scanning band 34 are turned on. The first data driver 46 and the second data driver 48 then respectively use the data line 38 and the data line 42 to transmit corresponding image data to the first row pixel units arranged in the first scanning band 32 and the first row pixel units arranged in the second scanning band 34.
When the application of the scanning signal for the first row scanning line 31 of the first scanning band 32 and the first row scanning line 41 of the second scanning band 34 is finished, the gate driver 44 supplies another scanning signal simultaneously to the second row scanning line 33 of the first scanning band 32 and the second row scanning line 43 of the second scanning band 34. At this time, the thin film transistors electrically connected with the first row scanning line 31 of the first scanning band 32 and the first row scanning line 41 of the second scanning band 34 are turned off, while the thin film transistors electrically connected with the second scanning line 33 of the first scanning band 32 and the second row scanning line 43 of the second scanning band 34 are turned on. Therefore, the first data driver 46 and the second data driver 48 are able to respectively use the data lines 38 and the data lines 42 to transmit corresponding image data to the second row pixel units arranged in the first scanning band 32 and the second row pixel units arranged in the second scanning band 34. By way of the above-described method, the pixel units arranged in the first scanning band 32 and the second scanning band 34 are sequentially scanned from the first row to the last row. When the scanning of the last row pixel units is completed, a frame is completely displayed by the liquid crystal display panel 30, a scanning signal is applied to the first row scanning line 31 of the first scanning band 32 and the first row scanning line 41 of the second scanning band 34 again, and so the next frame begins.
According to the prior art liquid crystal display panel 30 with dual scanning bands, the scanning lines of the first scanning band 32 and the second scanning band 34 are simultaneously scanned. Consequently, the scanning time required for a frame is reduced by half, and the problem of scan delay is prevented. For a liquid crystal panel comprising 1080 scanning lines and having a refresh frequency of 60 hertz (Hz), each scanning line has to finish scanning in 30.8 μs. However, the boundary 53 between the first scanning band 32 and the second scanning band 34 is easily observed by our vision, which results in a non-uniform image quality of the display panel 30.